The ability of a Vertical Take-Off-and-Landing (VTOL) Unmanned Aerial Vehicle (UAV) to land on uneven or sloped terrain is an unsolved challenge. In the mid-1990s, an Air-Mobile Ground Security and Surveillance System (AMGSSS), a multi-modal sensor package carried by the Sikorsky Cypher, a toroid-shaped UAV with counter-rotating rotors in the middle, was developed. The system was designed to fly and park on hilltops and rooftops, providing multi-day security sensing with video, infrared sensors, and motion detection capabilities. However, AMGSSS was only able to land on flat rooftops, severely limiting where it can perform its mission.
One idea presented here is to use onboard sensors to determine if the terrain below is flat and level enough for the UAV to land. The UAV can work by itself or in conjunction with a sensor-based terrain selection method, and can enhance the effectiveness of the terrain selection, allow operation on more rugged terrain, and allow greater margins of error.